1. Field of the Invention
The present invention relates to a speed governing apparatus that detects over-speed of an ascending/descending member, such as an elevator car or a counterweight, and stops the ascending/descending member, and an elevator system having the speed governing apparatus.
2. Description of Related Art
FIG. 1 is a longitudinal sectional view showing a conventional fly ball type speed governor disclosed in, for example, Japanese Unexamined Patent Publication No. 3-177283.
A system shown in FIG. 1 has a machine room 1 provided right above a hoistway, a speed governor 2 installed on the machine room 1, and an endless speed governing rope 3 which is disposed in the hoistway and one end of which is coupled to an ascending/descending member (not shown).
The system further includes a support member 4 of the speed governor 2, a horizontal shaft 5 rotatably held by the support member 4, a sheave 6 which is secured to the horizontal shaft 5 and onto which an upper end curved portion of the speed governing rope 3 has been wound, a perpendicular shaft 7 rotatably held above the support member 4, a driving bevel gear 8 that is secured to the horizontal shaft 5 and concentrically disposed to a rotational center of the sheave 6, and a driven bevel gear 9 that is secured to the perpendicular shaft 7 and in engagement with the driving bevel gear 8.
Reference numeral 10 denotes a well-known fly ball type speed governing mechanism provided on the perpendicular shaft 7. The fly ball speed governing mechanism 10 includes arms 11 having their upper ends pivotally held by an upper end portion of the perpendicular shaft 7, fly balls 12 secured to lower ends of the arms 11, a slide cylinder 13 fitted onto the perpendicular shaft 7, links 14 having both ends pivotally mounted on middle portions of the arms 11 and on the slide cylinder 13, and a balance spring 15 which is composed of a compression coil spring fitted to the perpendicular shaft 7 and disposed between the upper end of the perpendicular shaft 7 and the slide cylinder 13 to urge the slide cylinder 13 downward.
A driven cylinder 16 is fitted onto the perpendicular shaft 7, and pivotally attached to the slide cylinder 13 so that it is vertically moves as the slide cylinder 13 vertically moves; however, it does not rotate about the perpendicular shaft 7. A stop switch 17 is secured to the support member 4 and turns OFF the power of a driving unit (not shown) for driving the ascending/descending member. An operating lever 18 is secured to the driven cylinder 16 to operate the stop switch 17 as the driven cylinder 16 ascends.
The conventional fly ball type speed governor is disposed and constructed as described above, and as the ascending/descending member ascends or descends, the movement of the speed governing rope 3 causes the sheave 6 to rotate. This rotation is transmitted to the perpendicular shaft 7 via the driving bevel gear 8 and the driven bevel gear 9. The fly balls 12 revolve according to a rotational speed of the perpendicular shaft 7, and move up against the urging force of the balance spring 15 due to a centrifugal force.
As the fly balls 12 rise, the slide cylinder 13 and the driven cylinder 16 are displaced upward. If the rotational speed of the perpendicular shaft 7, that is, the ascending or descending speed of the ascending/descending member, exceeds a rated speed and reaches a first over-speed (the first over-speed is defined by the rated speed and represented by the code as ASME/ANSI A17.1-1987 SAFETY CODE FOR ELEVATORS AND ESCALATORS), the stop switch 17 is operated by the operating lever 18 to cut off the power of the driving unit of the ascending/descending member to thereby stop the ascending/descending member. If the ascending/descending member should be further over-speed downward due to some cause and reach a second over-speed from the first over-speed, an emergency stop unit (not shown) of the ascending/descending member is actuated, although detailed descriptions and illustrations thereof will be omitted.
FIG. 2 is a front view showing a conventional fly weight type speed governor disclosed in, for example, Japanese Unexamined Patent Publication No. 6-1564. FIG. 3 is a cross-sectional view of the fly weight type speed, governor.
The speed governor shown in the drawings include a base 21 having a U-shaped cross section, bearing boxes 22 which are disposed on side walls of the base 21 and in which bearings 23 are provided, a shaft 5 having its both ends rotatably supported by the bearings 23, a sheave 6 secured to the shaft 5, and fly weights 26 which are arranged to face each other on side surfaces of the sheave 6 via the shaft 5 and pivotally attached to the sheave 6, and weight sides thereof are rotationally displaced in a direction orthogonal to an axis of the shaft 5.
A balance spring 27 has one end thereof in engagement with an anti-weight side of the fly weight 26, while the other end thereof in engagement with a side surface of the sheave 6, and acts against a displacement of the fly weight 26 caused by the centrifugal force produced when the sheave 6 rotates. An actuating hook 28 is provided on the same side of the fly weight 26 where the balance spring 27 is in engagement. An actuating member 29 is composed of a bolt screwed in the weight side of the fly weight 26. A link 210 has its both ends disposed on opposite sides from each other with respect to pivoting points of the two fly weights 26.
A stop switch 211 is mounted on a base 21 and has an actuating assembly 212 opposed to the actuating member 29.
A ratchet 213 is rotatably held by the shaft 5 and disposed to face against the actuating hook 28. A brake arm 214 has its lower end pivotally attached to the base 21 and has a brake piece 215 attached to its middle portion. An actuating bar 216 has one end thereof pivotally attached in the vicinity of the rim of the ratchet 213, and a threaded bar on the other end thereof is movably inserted in an upper end portion of the brake arm 214, a spring shoe 217 being held by a nut 218 at an insertion end.
A compression coil spring 219 is fitted onto the screwed bar of the actuating bar 216, and disposed between the brake arm 214 and the spring shoe 217. The speed governing rope 3 is wound around the sheave 6, and one end thereof is retained on an ascending/descending member, such as a car, of an elevator system provided in a hoistway, although not shown in the drawings.
The conventional fly weight type speed governor is constructed as described above, and the sheave 6 rotates by being driven by the speed governing rope 3 that moves together with the ascending/descending member. As the sheave 6 rotates, the fly weights 26 revolve together with the sheave 6, and if the rotational speed of the sheave 6, that is, the speed of the ascending/descending member, reaches a first over-speed (the first over-speed is defined by the rated speed and represented by the code as ASME/ANSI A17.1-1987 SAFETY CODE FOR ELEVATORS AND ESCALATORS) that exceeds a predetermined value, a centrifugal force causes a rotational displacement of the fly weights 26 against the urging force of the balance spring 27. The rotational displacement of the fly weights 26 causes the actuating member 29 to press the actuating assembly 212 of the stop switch 211. This actuates the stop switch 211 to cut off the power of the driving unit of the elevator system so as to stop the ascending/descending member, thus preventing an accident caused by the occurrence of the first over-speed.
However, in case of an accident, such as breakage of a main rope of the elevator system, the ascending/descending member continues to descend even when the driving unit is stopped. In this case, if the ascending/descending member reaches a second over-speed (the second over-speed is defined by the rated speed and represented by the code as ASME/ANSI A17.1-1987 SAFETY CODE FOR ELEVATORS AND ESCALATORS), the actuating hook 28 engages a hook of the ratchet 213 due to the rotational displacement of the fly weights 26 produced by the centrifugal force against the urging force of the balance spring 27. As a result, the ratchet 213 circularly moves in the same direction in which the sheave 6 rotates, so that the actuating bar 216 is displaced, and, the brake arm 214 is moved via the compression coil spring 219 in the same direction in which the sheave 6 rotates. The brake piece 215 pushes the speed governing rope 3 against the sheave 6 to brake the descent of the speed governing rope 3. The brake of the speed governing rope 3 actuates the emergency stop unit of the ascending/descending member to bring the ascending/descending member to a halt. Hereinafter, a stopping operation of the driving unit and a stopping operation of the ascending/descending member by the emergency stop unit will be referred to as xe2x80x9can emergency stopping operationxe2x80x9d of an elevator car.
In the conventional fly ball type or the fly weight type speed governor as described above, the rotational direction of the sheave 6 changes according to the operating direction of the ascending/descending member. On the other hand, the centrifugal force produced in the fly balls 12 or the fly weights 26 is always in a direction opposite from the direction of the axial center of the perpendicular shaft 7 or the sheave 6 independently of the rotational direction of the sheave 6. Therefore, the amount of an upward displacement of the driven cylinder 16 or the amount of a rotational displacement of the fly weights 26 caused by the over-speed of the ascending/descending member is determined by an absolute value of the speed of the ascending/descending member. Hence, it is impossible to set different first over-speeds for different operating directions of the ascending/descending member.
There are some countries that have established regulations requiring that a vertical distance from a floor surface of the lowest level at which a car stops to a bottom floor surface of a hoistway, i.e., a pit depth, be set to not less than a value determined according to a rated speed of an elevator. This is because a size of a shock absorber installed in the pit differs according to rated speed. If, on the other hand, a pit depth is limited because of an architectural reason, then the rated speed of an elevator must be set to a value or less decided based on the pit depth. There is a demand, however, for setting only the rated speed for ascending, which is irrelevant to a possibility of a collision with the shock absorber, at a speed greater than a rated speed for descending in order to achieve efficient transportation.
However, if the conventional elevator speed governor is used that is capable of detecting only the same first over-speed regardless of the moving direction of the ascending/descending member as described above, then it would be impossible to exceed a maximum tolerance of a first over-speed specified by the regulations because of the rated speed in the descending direction, even when a rated speed for ascending is set to be higher than a rated speed for descending.
A sudden change in pressure in a car owing to high-speed operation causes uncomfortable feeling in passengers"" ears. This uncomfortable feeling is known to be more noticeable when the car descends than when it ascends. From this aspect also, demands arise for elevators having different rated speeds for ascending and descending.
The present invention has been made with a view toward solving the problems described above, and it is an object of the invention to provide an elevator system and a speed governing apparatus capable of detecting different values of first over-speed, depending on a moving direction of an elevator car.
According to one aspect of the present invention, there is provided an elevator system having: an elevator car that moves in a hoistway; a driving machine unit for moving the elevator car up and down via a cable; a control unit that controls the driving machine unit such that a moving speed at which the elevator car ascends is different from a moving speed at which the elevator car descends; and a speed governing unit for controlling a moving speed of the elevator car; wherein the speed governing unit has a first speed governing mechanism for detecting a moving speed of the elevator car when the elevator car ascends, and a second speed governing mechanism for detecting a moving speed of the elevator car when the elevator car descends; and speed control by the first speed governing mechanism or the second speed governing mechanism is invalidated, depending upon a moving direction of the elevator car.
In a preferred form of the present invention, the speed governing unit has a speed governing rope connected to the elevator car, a sheave on which the speed governing rope is wound and which rotates in a forward direction or a reverse direction as the elevator car moves up or down, and a transmitting mechanism for controlling engagement and disengagement of transmission of a torque of the sheave to the first speed governing mechanism or the second speed governing mechanism according to a rotational direction of the sheave.
In another preferred form of the present invention, a first over-speed in an ascending mode and a first over-speed in a descending mode are set as threshold values for starting an emergency stop operation of the elevator car, a value of the first over-speed in the ascending mode and a value of the first over-speed in the descending mode are different from each other, and the first speed governing mechanism detects the first over-speed in the ascending mode, while the second speed governing mechanism detects the first over-speed in the descending mode.
In a further preferred form of the present invention, a second over-speed in the descending mode is set to a value as a threshold value for starting the emergency operation of the elevator car that is larger than the value of the first over-speed in the descending mode, and the second speed governing mechanism detects the second over-speed in the descending mode.
In yet another preferred form of the present invention, the first over-speed V1 in the ascending mode, the first over-speed V2 in the descending mode, and the second over-speed V3 in the descending mode have a relationship represented by V1 greater than V3 greater than V2.
In a further preferred form of the present invention, the first over-speed V1 in the ascending mode, the first over-speed V2 in the descending mode, and the second over-speed V3 in the descending mode have a relationship represented by V3 greater than V1 greater than V2.
In a further preferred form of the present invention, the speed governing unit has a speed governing rope, a sheave on which the speed governing rope is wound and which rotates as the speed governing rope moves, a first speed governing mechanism that governs a rotational speed of the sheave, and a second speed governing mechanism that controls a rotational speed of the sheave when the sheave rotates in a forward direction, while it stops speed control when the sheave rotates in a reverse direction.
In a further preferred form of the present invention, the sheave and the second speed governing mechanism are connected via a transmitting mechanism for transmitting the rotation of the sheave, and the transmitting mechanism transmits the rotation of the sheave to the second speed governing mechanism when the sheave rotates in the forward direction, while the transmitting mechanism disengages the transmission of the rotation of the sheave to the second speed governing mechanism when the sheave rotates in the reverse direction.
In a further preferred form of the present invention, the first speed governing mechanism is a fly weight type speed governor.
In a further preferred form of the present invention, the second speed governing mechanism is a fly ball type speed governor.
In a further preferred form of the present invention, the transmitting mechanism is a clutch coupled between a rotating shaft of the sheave and a rotating shaft of the second speed governing mechanism.